1. Field of the Invention
The present invention relates to a data position data feedback device, and more particularly to a linear feedback device for an actuator that utilizes the gear ratio between the return gear wheel and the driven teeth to adjust the back and forth moving distance of the probe. The present invention can be used as an external hanging type equipment and offer an absolute position sensing function while preventing the error accumulation.
2. Description of the Prior Art
Nowadays, linear actuators are applied more and more widely in industrial field, and particularly in the high precision mechanism. The linear actuators must be provided with precision position data linear feedback device in order to accurately control the high precision mechanism. Hence, it is self-evident that the actuator is very important to the existing various industrial mechanisms.
Most of the current linear actuators suitable for use in high precision equipments are usually provided with three types of position data feedback devices, they are: linear potential feedback device, magnetic induction feedback device, and rotary feedback device, and their respective techniques are described as follows:
Linear potential linear feedback device is a technique of calculating the position by converting linear position change into adjustable resistance value. When the linear potential linear feedback device moves along with linear actuator, it will move the spring leaf for contacting the internal adjustable resistor, consequently changing the resistance value and the outputted voltage signal, thus achieving the function of calculating the displacement of the linear potential feedback device. As shown in FIG. 1, a conventional linear potential linear feedback device comprises a rod-shaped body 10, a driven rod 11 and a transmission belt 12. The body 10 is positioned on the actuator 13 and located along the moving direction thereof, the driven rod 11 is disposed on the body 10 is connected to the end of the moving assembly 131 of the actuator 13 via the transmission belt 12. When the moving assembly 131 of the actuator 13 moves, the transmission belt 12 will drive the driven rod 11 to move relative to the body 10, thus changing the resistance value of the body 10 and the position of the spring leaf. This conventional technique still has the following disadvantages:
First, since the length of the driven rod 11 and the body 10 must be in accordance with the travel length of the moving assembly 131 of the actuator 13, the body 10 of the linear potential linear feedback device is relatively long and is space consuming.
Second, since the length of the driven rod 11 and the body 10 must be in accordance with the travel length of the moving assembly 131 of the actuator 13, a to and fro movement of the moving assembly 131 will cause a relatively large amount of wear to the resistor and the spring leaf.
Third, since the travel length of the moving assembly 131 of the actuator 13 determines the entire length of the conventional linear actuator, the size of the linear potential linear feedback device for each actuator 13 has been fixed, the linear potential feedback devices of different sized linear actuators 13 are not interchangeable. Therefore, the linear potential linear feedback device is unsuitable for mass production and cannot be used as an external hanging type accessory to different sized linear actuators 13.
To solve the abovementioned disadvantages, magnetic induction linear feedback device and rotary linear feedback device appeared on the current market, their respective techniques and problems are explained as follows:
The magnetic induction linear feedback device has a rotary disc disposed on the rotary end of the motor inside the linear actuator, around the outer periphery of the rotary disc is annularly arranged a plurality of magnetic members, another sensor rotating along with the motor serves to detect the polarity of the respective magnetic member passed by. This conventional technique has the advantage of non-contact and can improve the problem of the size being restricted by the travel length. However, the problem is that the feedback signal can only feedback the relative position, so that he software is complicated and difficult to control. Further, the annularly arranged magnetic members still produces induction sectors, it not only has the problem that the displacement within the same sector cannot be calculated accurately, but the errors of the respective magnetic members will be accumulated along with the accumulation of rotation.
The rotary linear feedback device has a contact-type rotary potentiometer mounted on the rotary end of the motor and doesn't have the problem of the error accumulation, induction sector, and the travel length restriction, but it has the problem of abrasion. Further, the rotary linear feedback device must be connected to the motor, therefore, not only the interior connection and the spatial position should be considered comprehensively when designing the interior, but also the rotary potentiometer must be assembled in the actuator during the assembly process and is difficult to disassemble. Therefore, the user can't choose to assemble or not to assemble, further, it impossible to produce hanging type accessory product for this type of rotary feedback device.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.